EP1129485B1 - Electronic component and use of a protective structure contained therein - Google Patents

Abstract

An electronic component is described and has a dielectric layer which is constructed on a substrate, conductive surfaces that are constructed on the dielectric layer, and an electrically conductive guard structure. The guard structure is disposed in a plane above the conductive surfaces such that the conductive surfaces are not completely covered by the guard structure.

Description

The invention relates to an electronic component and the use of a protective structure provided in the electronic component as protection against electrostatic discharge. So far, electronic components have usually been provided within a housing from which lead out supply lines for supplying the power supply or for supplying and / or discharging signals. In these electronic components, in particular, those containing a semiconductor chip inside the package made in so-called CMOS technology are very sensitive to electrostatic discharge. It comes in the device by externally acting on the component potential differences to charge shifts, which ultimately leads to an overvoltage on one or more of the so-called. Gate capacitors, so that here it leads to a direct discharge between the individual plates of said gate capacitor comes, which usually leads to the destruction of the component. Such an electrostatic charge, which then discharges destructively, may be caused, for example, by contact, and protection against this is afforded in electronics laboratories, for example, by mounting the components on a conductive foam rubber. Furthermore, often carry people who come into contact with these components in electronics laboratories corresponding grounding straps, so that by touching no charging can occur. For the production by means of assembly systems, in which the components are mounted on printed circuit boards, appropriate precautions are provided.

Once the components have been installed in a circuit, there is usually only a slight risk of destroying the component by electrostatic discharge. However, this can always be done by circuit errors or defects of other components. In order to avoid this, electronic components generally have additional circuit protection structures, so that there is protection against electrostatic discharges (ESD protection) as well as against supplied overvoltages. These are usually surges of laxative circuits.

A fundamental disadvantage of such an ESD protection is that it costs "chip area" which does not contribute anything to the actual functionality of the electronic component. Another disadvantage of such ESD protection is that it often changes the functionality of the device without this ESD protection. Due to the ESD protection, there is often a reaction to the sensitivity and / or dynamics of the component.

New electronic components today have no closed housing, so that parts of the semiconductor chip are exposed to the outside. These new electronic components are, for example, so-called "chip size packages" (CSP), in which the chip with its contacts is mounted directly on a printed circuit board. Furthermore, various sensors are increasingly being manufactured as semiconductor devices. Both in CSP and when used as a sensor, the device has a total or at least a proportionately relatively large area to the environment freely accessible.

In these cases, there is an increased need for protective measures against electrostatic discharge. Such components are also fingerprint sensors, which consist of a matrix of many individual capacities. It is provided that the finger, from which an impression is to be taken, directly touches the component. Especially in such a case, a static charge can easily occur because in the normal use of such a sensor, it is unacceptable for the finger to be grounded for discharge before use. Even with mobile devices in which a fingerprint sensor is provided, for example in a cell phone, the risk remains that it comes by carrying around the device to an electrostatic charge.

From WO 98/52157 a fingerprint sensor device is known in which an electrically conductive layer is arranged under a ground plate.

Furthermore, it is known from US Pat. No. 5,325,442 to arrange a grounded strip-shaped conductive layer in the spaces between conductive plates in the longitudinal direction, which is intended to protect against electrostatic discharges. The same applies to EP 09 02 387 A2 (post-published)

The invention is now based on the object to provide an electronic component, in which even if a considerable part is not surrounded by a housing, a secure ESD protection is provided. This object is achieved with the means specified in claim 1 and 7, respectively.

By providing an electrically conductive protective structure disposed in a plane above conductive surfaces and leaving the conductive surfaces exposed, it is ensured that by appropriate connection of the conductive protective structure, this has the effect of a Faraday cage. This ensures protection against electrostatic discharge in a simple manner.

Further advantageous embodiments are specified in the subclaims.

By providing a gap region, there is no coverage of the conductive surfaces by the protective structure. The strip-shaped, oblique forming of the protective structure leads to the gap areas directed non-planar ends having the effect of a lightning arrester.

By using tungsten to make the protective structure, it is highly durable.

The formation of the protective structure in a structure width of 1 μm-5 μm is particularly easy to handle. Furthermore, the formation of a grid-like protective structure combines easy manufacturability with high efficiency as ESD protection with minimized material requirements.

Fig. 1

ein erstes erfindungsgemäßes Ausführungsbeispiel,

Fig. 2

ein zweites erfindungsgemäßes Ausführungsbeispiel,

Fig. 3

die in Fig. 1 und 2 dargestellten Ausführungsbeispiele in einer Draufsicht,

Fig.4

eine vorteilhafte Ausgestaltung des in Fig. 1 dargestellten Ausführungsbeispiels,

Fig. 5

eine weitere vorteilhafte Ausgestaltung des in Fig. 1 dargestellten Ausführungsbeispiels, und

Fig. 6

wesentliche Verfahrensschritte zur Herstellung des erfindungsgemäßen elektronischen Bauelements.

The invention will be explained with reference to the drawings based on embodiments. Show it:

Fig. 1

a first embodiment according to the invention,

Fig. 2

a second embodiment according to the invention,

Fig. 3

the embodiments shown in FIGS. 1 and 2 in a plan view,

Figure 4

an advantageous embodiment of the embodiment shown in Fig. 1,

Fig. 5

a further advantageous embodiment of the embodiment shown in FIG. 1, and

Fig. 6

essential process steps for the production of the electronic component according to the invention.

In the following description, like reference numerals indicate like parts.

In Fig. 1, the electronic component according to the invention is shown schematically. In this case, a dielectric layer 2, which is provided for separating active or conductive structures of contact surfaces or overlying conductive surfaces, is located on the surface 1 of a semiconductor chip. Such a conductive surface 4 or 4 'is directly formed in the illustrated embodiment on the dielectric layer 2, wherein spaces between the electrically conductive surfaces 4 and 4' filled with an oxide 3 are that the electrically conductive surfaces 4 and 4 'also separated from the overlying nitride layer 5.

In the illustrated embodiment, the electrically conductive surfaces 4 should be individual sensor elements of a fingerprint sensor. In this case, the electrically conductive surfaces 4 each represent a capacitor surface, while the finger as such forms the opposite capacitor surface. The electrically conductive surfaces 4 'are, for example, lines, wherein the connections are not shown. On the oxide 3, in turn, a nitride layer 5 is formed, which may also be composed of several layers. In the nitride layer 5 recesses are provided, which are filled with tungsten. Now, the arrangement is such that a finger F, whose impression is to be scanned, and which is to be placed on the surface of this structure, with the electrically conductive surfaces 4 further forms a capacitor, since the tungsten structure 6 in the intermediate regions Z, between the electrically conductive surfaces 4 is arranged. If the finger F is electrically charged, then this is discharged when the tungsten structure 6 is grounded, as indicated in Fig. 1.

In the illustrated embodiment, the fingerprint sensor has a suitable structure in which the oxide surrounding the conductive areas 4 has a thickness of approximately 250 nm, the nitride has a thickness of 1500 nm, the depth of the recesses for the tungsten structure 6 is approximately 370 to 700 nm, and the width of the recesses is about 1 micron.

In Fig. 2, the use of the tungsten structure 6 is shown in a surface mount electronic device as in CSP. Here, a conductive surface 14 formed in an oxide is exposed to the surface through the protective nitride 5 therethrough. The thus forming Opening 7 serves to contact the conductive pads 14 serving as a contact pad in surface mounting on a printed circuit board. In this case, the opening 7 is then filled with a solder or a conductive adhesive. Again, on the surface of the tungsten structure 6 is formed, which will approach in normal use no charged finger in the assembled state, however, it is easily possible in the usual operation of a CSP mounted device that it on the surface of the circuit board to an electrostatic Charge is coming. The conductive protective structure 6, which is also formed in the illustrated embodiment as a tungsten structure, also serves here when it is grounded as protection against electrostatic discharge. It acts as it were for the component as a Faraday cage. The use of tungsten is not mandatory, but compared to other AL alloys currently used in semiconductor technology, tungsten has a maximum current density increased by a factor of 6 and the melting point of tungsten, at 3410 ° C., is significantly higher than that of a conventional aluminum alloy (AlSiCu / 660 ° C).

In both FIG. 1 and FIG. 2, the tungsten structure 6 is formed above conductive surfaces 4 'lying in the same plane as the conductive surfaces 4. This is chosen because the conductive surfaces 4 'need not be accessible from outside.

This is again shown in Fig. 3 viewed from above. Here, the conductive surfaces 4 and 14 are shown. It is omitted in this illustration on cover layers. That is, the conductive surfaces 4 as contact surfaces 14 as described with reference to FIG. 2 as well as the capacitor plate 4 will be described with reference to FIG. Between these conductive surfaces 4 and 14, the conductive tungsten structure 6 is lattice-shaped as seen from above formed, wherein it is obliquely aligned with the side surfaces of the conductive surfaces 4 and 14 respectively. As a result of the lattice formation, and in that the lattice does not cover the conductive surfaces 4 or 14, projections or tips, which are particularly well suited for protection against electrostatic discharge, form at the edges in the structure. This grid structure thus has at the edges to the conductive surfaces 4, a similar effect as lightning conductors. Between the conductive surfaces 4 and 14, as already shown in FIGS. 1 and 2, conductive surfaces 4 'are shown, which are covered by the tungsten grating 6, since the conductive surfaces 4' do not have to be accessible upwards.

With reference to Fig. 4 and 5, an advantageous embodiment of the invention is shown in particular as a fingerprint sensor. The same elements are provided with the same reference numerals. The fingerprint sensor, which is shown in a section, consists of a substrate 10, on the surface of which an active structure in the form of an integrated circuit may be formed, but need not necessarily be present for the present invention. Above this, on a part of the substrate surface, there is a structure of polysilicon 9, which in turn is covered with a boron-phosphorus-silicon-oxide glass layer 8. Above this there is a first metallization layer with metallization paths, which are not described in greater detail, and which are covered by a dielectric layer 2. This is the same dielectric layer as already known from the illustration according to FIG. 1 or FIG. 2. The overlying structure corresponds to the structure of FIG. 1 or FIG. 2. The entire component in turn is surrounded by a housing 11, which leaves a surface of the device, but it is pulled around the edge so that it rests on the surface ,

According to FIG. 4, vias are provided by the surface through all the layers described above up to the substrate, which is connected to ground. The lying on the surface part of the via is in turn electrically connected to the tungsten structure 6. In this way, also an arrangement corresponding to a Faraday cage is provided. The frame surrounding the exposed chip surface of the housing 11 is provided with a ground frame 12.

In contrast to this, according to FIG. 5, no through-connection through all layers is provided. In the embodiment shown here, the tungsten structure 6 is electrically conductively connected to the ground frame 12. Otherwise, the underlying structures are again through-contacted with each other in the edge region and then the ground connection takes place via the substrate. Also in this illustrated embodiment, a Faraday cage is provided in this way.

In a modification of the embodiment shown in Fig. 5, the connection between the ground frame and the tungsten structure 6 can also be generated via a conductive adhesive. For this purpose, as shown in Fig. 5, the ground frame 12 must be pulled around so far that it rests on the tungsten structure 6. It suffices to connect the arrangement of the mass frame 12, similar to that shown in FIG. 4, to the tungsten structure 6 via a conductive adhesive connection 13 in the proximity region (see FIG. 5 a).

According to Fig. 6, the production of the tungsten structure is shown schematically. First, there is a planarization of the structure, which results from the conductive surfaces 4, or 14 or 4 'and the oxide 3 surrounding these surfaces. On this structure, the nitride is applied, which is treated lithographically, followed by a Nitridgrabenätzung for the formation of the recesses described above is performed. Subsequently, tungsten is applied by means of a CVD process step (chemical vapor deposition). The tungsten, which is applied over the whole area, is then removed down to the height of the nitride layer. The different removal processes shown in I and II lead to different waviness of the structure. In the lower part of Fig. 6, in contrast to the upper part of the starting structure of the conductive surfaces and the oxide surrounding the conductive surfaces so flat that also forms a planar nitride layer.

Depending on the technology used, a structure width between 1 and 10 μm can be provided for the tungsten structure. In CSP devices that are not exposed to the extreme case that an electrostatically charged finger approaches the surface, it may also be useful not to form a lattice structure, but that simply part of the surface is covered over the entire surface with tungsten.

However, the invention described above is not limited to semiconductor devices only. It is equally applicable to future technologies such as electronic circuits in polymer switch technology. The invention is particularly advantageous when these components are freely accessible as sensors, with fingerprint sensors are only an example. Such an application can already be predicted, for example, for use on smart cards, where there is a desire for resilient, elastic and protected against environmental influences fingerprint sensors to reliably determine the identity of the user can.

Claims (7)

1. Electronic component having a dielectric layer (2) which is formed on a substrate (10), conductive areas (4; 14) which are formed on the dielectric layer, and an electrically conductive protective structure (6) which is arranged in a plane above the conductive areas (4; 14) in such a manner that the conductive areas (4; 14) are not completely covered by the protective structure (6) and the protective structure (6) is arranged along interspace regions (Z) which are formed between the conductive areas (4; 14), characterized in that the protective structure (6) runs, in the form of a strip, obliquely with respect to a propagation direction of the interspace region (Z).
2. Electronic component according to Claim 1, in which the direction in which the protective structure (6) in the form of a strip runs changes at the edge of the interspace region (Z) in such a manner that the interspace region (Z) is not left, or changes at the edge of the interspace region (Z).
3. Electronic component according to one of the preceding claims, in which the protective structure (6) is formed from tungsten.
4. Electronic component according to one of the preceding claims, in which the protective structure (6) has a structure width of 1 µm to 5 µm.
5. Electronic component according to one of the preceding claims, in which the protective structure (6) is in the form of a lattice.
6. Electronic component according to one of the preceding claims, in which one of the conductive areas (4; 14) is part of an individual sensor element.
7. Use of the protective structure (6) comprising one of the electronic components according to one of the preceding claims as an apparatus for protecting against electrostatic discharge.

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